plant innate immunity - university of maryland college of...

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Plant Innate immunity

Shunyuan XiaoCenter for Biosystems Research

University of Maryland Biotechnology InstituteEmail: [email protected]

Introduction to plant innate immunity

Diversity and conservation of plant R genes

Plant-pathogens recognition

R protein regulation and signal initiation

Signaling pathways of plant resistance

The SA-dependent pathway

Crosstalk between SA-pathway and other pathways

Food for:

Human

Animals

Insects

Micro-organismsVirusesBacteriaFungiNematodes…..

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Powdery mildew

Bacterial speck

Spotted wilt

Anthracnose

Mosaic virus

Fusarium wilt

Crown gall

Root Nematode

Caterpillar

Plants face challenges from various herbi-vores and microbes at all stages and in all organs

Powdery mildew

Bacterial speck

Spotted wilt

Anthracnose

Mosaic virus

Fusarium wilt

Crown gall

Root Nematode

Biotrophic (co-survive)

Necrotrophic (kill)

Hemi-biotrophic (Let

alive first and then kill)

Pathogens

Because plants have evolved defense systems to protect themselves !!!

Most plants are resistant to most potential pathogens in most times !!!

Nonhost Resistance

Host Resistance

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• Acts at the species level• A major contribution to safety of plants• More evolutionarily ancient • Multi-layered (therefore complicated)

Nonhost Resistance

• Part of it is activated upon recognition of generalfeatures of microbes called MAMPs (Microbe-associated molecular patterns) such as EF-Tu, Flagellin, and LPS----Basal Resistance

MAMP-triggered Immunity (MTI)

Cell 125:749-960 (2006)

Molecular Cell 5:1003-1011 (2000)

Host Resistance

• Acts under the species level (some cultivars areresistant some are susceptible)

• More recently evolved (after the breakdown ofnonhost resistance) to counteract pathogen suppression of MTI by specific effectors.

• Controlled by single or a few polymorphic host genes, i.e. resistance (R) genes that recognizepathogen effectors.

Effector-triggered Immunity (ETI)= R-gene resistance

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Stage I Stage IIIStage II

Evolution of the plant innate immune system

Chisholm et al, Cell 124: 803-814 (2006)

Nonhost (basal) resistance Susceptibility Host (R-depend) resistance

Isolated Plant R genes in the past 15 years

KINTMeLRR KINTMeLRR

eLRR TMeLRR TM

TIR LRRNBSTIR LRRNBS

CC LRRNBSCC LRRNBS

Schematic domain structures

Functions Protein Classes

Plant Immunity

NBS-LRR

eLRR

Plant Immunity

Plant Immunity

Plant Immunity

Plant Immunity

NBS Nucleotide binding site

LRRLeucine rich-repeat

TIRToll interleukin receptor

PKProtein Kinase

CCCoiled coilTMTransmembrane

LRRNBSCARD LRRNBSCARD

TMeLRR TIRTMeLRR TIRToll / TLRs

Nod1 / Nod2

Animal Immunity

Animal Immunity

FLS2; EFR

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NBNB

NB

CC

Nurnberger, Immunological Reviews, 198: 249–266 (2004)

Striking similarity and obvious difference between plant and animal innate immunity

KINTMeLRR KINTMeLRR

eLRR TMeLRR TM

TIR LRRNBSTIR LRRNBS

CC LRRNBSCC LRRNBS

Schematic domain structures

Protein Classes

Plant Immunity

NBS-LRR

eLRR

Plant Immunity

NBS Nucleotide binding site

LRRLeucine rich-repeat

TIRToll interleukin receptor

PKProtein Kinase

CCCoiled coilTMTransmembrane

KINKIN CCTM CCTM

TM TMTM TMAtypical

(Pto)

(Xa13)

(Xa27)

(RPW8)

TMTM TMTM TMTM TMTM TMTM TMTM TMTM TMTM

Cellular signaling events of plant defense

Path

ogen R

Cell wall deposition

Ca++ K+

H+

Salicylic acid accumulation

MAP Kinase Activation

Activation of NADPHOxidase complex

ROS production

Synthesis of antimicrobialCompounds;HR Cell death Local response

Activation of systemic acquired resistance

Nitric oxide production

Redox change

Activation of transcription factors

Expression of defense-related genes

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Compatible Interaction

Incompatible Interaction

Molecular mechanisms of R-mediated disease resistance

R

Avr (effector)

HR and PR expression

Activation of defenses locally and systemically

Recognition

Signalinitiation

Signaltransduction

Step 1

Step 2

Step 3

Step 4

R*

Step 1: Plant-pathogen Recognition

R

Plant

Avr

Pathogen

HR cell death, PR gene expression and other defence responses

The “gene-for-gene” model (Flor, 1956)

Key Player

Key Player

DiseaseDisease-AvrDiseaseResistanceAvr

-RR

DiseaseDisease-AvrDiseaseResistanceAvr

-RR

Avr = effector

Direct R-Avr Interaction

Pto / AvrPtoPita / AvrpitaRRS1-R / popP2

Science, 274:2060-2063

Embo J, 19:4004-4014

PNAS, 100:8024-8029

PNAS 103:8888-93 (2006)

L(5/6/7) / AvrL(5/6/7)

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Indirect R-Avr interactionMost R and Avr do not seem to have direct interaction

Pto (kinase) requires Prf (CC-NBS-LRR) for function

RPP5 (CC-NBS-LRR) requires PBS1(kinase) for function

Number of pathogen Avr genes >> number of R genes

Guard hypothesis (Van der Biezen and Jones 1998 ; Jones and Dangl 2001)

NBS-LRR(other R)

Host protein(kinase or others)

Pathogen effector(avirulence protein)

Guard Guardee Attacker

Activation of Defenses1

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Indirect R-Avr Interaction: The Guard Hypothesis

RPS2(CC-NBS-LRR)

RIN4 AvrRpt2

RPS5(CC-NBS-LRR)

PBS1(kinase)

AvrPphB

Cf2(RLP)

Rcr3(cysteine protease)

Avr2

Degradation

Cleavage

Inhibition

RPM1(CC-NBS-LRR)

RIN4 AvrRpm1, AvrB

Guard Guardee Pathogen effectorPhosphorylation

Prf(CC-NBS-LRR)

Pto(kinase)

AvrPtoConformationalChange ?

Recognition of pathogen by R genesExample: RPS2---RIN4---AvrRpt2

Schulze-Lefert, Science 308, 506-508 (2005)

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TIR

LRR

NBS

CC

Defenses

Two modes of plant-pathogen recognition

Pathogen effectors

TIR

LRR

NBS

CC

Defenses

Direct Recognition Indirect Recognition

Plasma Membrane

Basal Defense

??




R

Avr


Activation of defenses

Recognition

Signalinitiation

Signaltransduction

Step 1

Step 2

Step 3

Step 4

R*

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ActiveInactive

Guardee(host target)

Guard (NBS-LRR)

Avr

Other partners

Dangl & Jones NATURE, 411:826-833 (2001)

ActiveInactive

Step 2: R protein regulation and signal initiationInter-molecular interaction

Step 2: R protein regulation and signal initiation

Guardee(host target)

Guard (NBS-LRR)

RAR1

SGT1

Hsp90 RAR1: A component required for function of many NBS-LRRs; Plays a role in R protein accumulation.

SGT1b: Interacts with RAR1; Required for function of some NBS-LRR genes; Two separable functions (1) a positive role in R-triggered cell death (2) A negative role in NBS-LRR (RPS5) accumulation.

Hsp90: A chaperone protein required for proper folding of NBS-LRR proteins.

Ready for activation or degradation ??

Inter-molecular interaction

Intra-molecular interaction of NBS-LRR proteins

CC LR

R

NBSCell death Cell death

CC LR

R

NBS

AVR

CC LR

R

NBSCell death Cell death

CC LR

R

NBS

Hwang et al, Plant Cell, 12, 1319-1330 (2000)

CC LRRNBSMi-1.1

CC LRRNBSMi-1.2

Non-functional Functional CC LRRNBS

Mi-1.1/Mi-1.2

Constitutive active


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Intra-molecular interaction of NBS-LRR proteins (Rx of potato)

Moffett et al, EMBO 21:4511-4519 (2002)

Rairdan et al, Plant Cell 18:2082-2093 (2006)

CCNBS (ADP)

LRR

Physical Interactions

CC / NBS-LRR

CC-NBS / LRR


CC

NBS (ATP)LRR

Takken et al, Curr Opin Plant Biol, 9:383-390 (2006)

Intra-molecular interaction of NBS-LRR proteins (Rx of potato)

Moffett et al, EMBO 21:4511-4519





R

Avr


Activation of defenses

Recognition

Signalinitiation

Signaltransduction

Step 1

Step 2

Step 3

Step 4

R*

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PAD4SAG101

Salicylic acid

EDS5

SID2

NPR1-dependent and independent signaling

SA-dependent feedback loop and basal resistance EDR1

LSD1

Basal resistance

Defense against biotrophsor hemi-biotrophs

Two branches at an early step

PathogenPathogen

EDS1

TIR NBS LRR

PathogenPathogen

NDR1

CC NBS LRR

Signal transductionStep 3:

NPR1

Systemic Acquired Resistance

HR cell deathPR expression

TGAs

DIR

PAD4SAG101

Salicylic acid

EDS5

SID2

NPR1-dependent and independent signaling

SA-dependent feedback loop and basal resistance EDR1

LSD1

Basal resistance

Defense against biotrophsor hemi-biotrophs

Two branches at an early step

PathogenPathogen

EDS1

TIR NBS LRR

PathogenPathogen

NDR1

CC NBS LRR

?

Signal transductionStep 3:

NPR1

Systemic Acquired Resistance


TGAs

DIR

RIN4

RIN4 (host target) interacts with NDR1

Cellular signaling events of plant defense responses

Path

ogen R

Cell wall deposition

Ca++ K+

H+

Salicylic acid accumulation

MAP Kinase Activation

Activation of NADPHOxidase complex

ROS production

Synthesis of antimicrobialCompounds;HR Cell death Local response

Activation of systemic acquired resistance

Nitric oxide production

Redox change

Activation of transcription factors

Expression of defense-related genes

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Mou et al, Cell, 113:935-944 (2003)Pieterse and Van Loon, Current Opinion in Plant Biology, 7:456-464 (2004)

How NPR1 works

COI1

JasmonicAcid

PathogenPathogen

PDF1.2 expressionResistance

?

JAR1

Ethylene

EIN2

PathogenPathogen

EDS1PAD4

Salicylic acid

EDS5

PathogenPathogen

NDR1


SAG101

SID2EDR1

LSD1

NPR1TGAs

TIR NBS LRR CC NBS LRR

Defense against biotrophs Defense against necrotrophs

MPK4

WRKY70

BIK1

bacteria

Defense against bacteria

Pathogen

flagellin

MAPKKK

MAPKK

MAPK

WRKY

Basal resistance

FLS2

Shen, Q.H. et al. Science, published online December 21, 2006

Barley Cell

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Barley Cell

Pathogen effectors suppress basal resistance

Pathogen effectors

LRR

NBS

CC

DefensesIndirect Recognition

Pto

Plasma Membrane

Prf

Basal Defense

??

Mucyn et al, Plant Cell 18:2792-2806 (2006)

avrPtoavrPtoB

Pathogenbacteria flagellin

FLS2

MAPKKK

MAPKK

MAPK

WRKY

Basal resistance

He et al, Cell 125:563-575 (2006)

Navarro et al, Science, 312:436-439 (2006)

Flagellin-inducible miR393 contribute to basal resistance by targeting auxin-receptors and repressing auxin-signaling


FLS2

MAPKKK

MAPKK

MAPK

WRKY

Basal resistance

miR393 TIR / AFB2 / AFB3

Auxin-signaling

Auxin responses

Auxin

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Melotto et alCell 126, 969–980 (2006)

Coronatine

ABA

Nitric oxide OST1 kinase

Stomatal closure

Cytoplasm

Epidermal surface Flagellin or LPS

Guard Cell

COI1

Katiyar-Agarwal et al, PNAS, October 27, 2006

Flagellin-inducible miR393 contribute to basal resistance by targeting auxin-receptors and repressing auxin-signaling


FLS2

MAPKKK

MAPKK

MAPK

WRKY

Basal resistance

ABA-mediated stomatal closure

miR393 TIR / AFB2 / AFB3

Auxin-signaling

Auxin responses

Summary

• Plants evolved non-host and host (R –gene) resistance

• R proteins recognize Avr protein through direct or indirect interaction

• R proteins may forms protein complexes with other proteins

• Intra-molecular interaction may play a role in R proteinactivation

• R genes mainly signal through the SA pathway

• The defense pathways have crosstalks with manyother signaling pathways

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CBR I Center for Biosystems Research

Molecular Basis of RPW8-mediated Broad-spectrum resistance in Arabidopsis

Col-0

Arabidopsis + Powdery mildew (Erysiphe)

Ms-0

Compatible interaction between Arabidopsis and Erysiphe

12 h 24 h

6 d

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Incompatible interaction between Arabidopsis and Erysiphe

12 h 24 h

6 d

The RPW8 Gene Cluster

Xiao et al, Science 291:118-120 (2001)

RPW8.1 RPW8.2 HR3 HR2 HR1

Ms-0

RPW8.1 RPW8.2 HR3 HR2 HR1

Ms-0

Col-0

1 kbHR4

Col-0

1 kbHR4

RPW8 is a unique R gene

CCTM CCTM1. Atypical protein structure

2. Conferring non-race specific resistance

3. Function in heterologous background

~20 KD

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RPW8

CCTM

InteractionPartners

ProteinProperties

Origin &Evolution

SignalingPathway

Erysiphe

EDS1

NPR1

PAD4

EDS5

Salicylic Acid

HR cell death & Broad-Spectrum Resistance

RPW8

EDR1

TIR-NBS-LRRHR3

? 14-3-3 PP2C

ERH1

At Shady Grove

plant innate immunity - university of maryland college of...

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